metamorphic
Quartzite Pebble
Metamorphosed Quartz-rich Sandstone
Hardness: 7 (Mohs scale), Color: tan-yellow to beige with brown staining, Luster: dull to vitreous, Structure: granular (granoblastic), Cleavage: none (conchoidal fracture).
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Physical properties
Hardness: 7 (Mohs scale), Color: tan-yellow to beige with brown staining, Luster: dull to vitreous, Structure: granular (granoblastic), Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure caused individual quartz grains to recrystallize and fuse together, creating a very durable rock.
Uses & applications
Usually used as decorative gravel, in construction aggregate, or as railroad ballast. Smaller smooth pebbles are often used in landscaping.
Geological facts
Quartzite is so tough that unlike sandstone, which breaks around its grains, quartzite breaks through its grains. It is highly resistant to chemical weathering.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade) and lack of reaction to acid. Commonly found in riverbeds, glacial tills, and coastal deposits worldwide.
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